1. Field of the Invention
This invention relates to a Metal-Insulator-Semiconductor-type (MIS-type) semiconductor device, and more particularly to a semiconductor device having a silicide film above the source-drain diffused layer regions and a method of manufacturing the semiconductor device.
2. Description of the Related Art
In recent years, MIS-type Field-Effect Transistors (FETs) have been required to provide improved element characteristics, particularly higher operating speed and lower power consumption. To speed up FETs, it is necessary to improve the current driving power of the component elements.
In conventional FETs, a reduction in the gate length has improved the current driving power. With the recent progress in miniaturization, however, only the reduction of the gate length has no longer assured a sufficient improvement in the current driving power. For this reason, the current driving power is requested to be improved by another method. As an example, a method of improving the mobility of carriers by applying a stress to the channel region of an FET has been used.
A configuration to apply a stress to the channel region is a structure that sandwiches a channel region with semiconductor materials whose lattice constant differs from that of the channel region. Specifically, silicon-germanium (SiGe) whose lattice constant is slightly larger than that of silicon (Si) is embedded in the source-drain (diffused layer) region of a p-channel MOSFET. Then, the stress produced by the difference in lattice constant between Si and SiGe is used. The substrate used to form elements is n-type Si. On the source-drain diffused layer region, an NiSi film is formed to decrease resistance.
In this type of semiconductor device, the following phenomenon occurs: the NiSi film formed on the source-drain diffused layer region projects into the Si substrate. When the NiSi film has projected into the substrate, the NiSi film comes into contact with not only the p-type SiGe region but also the n-type Si substrate. In this case, when a voltage is applied to the source-drain diffused layer region, a problem occurs: current flows from the NiSi film to the n-type Si substrate.